# Thread: HA in relation to STA

1. ## HA in relation to STA

Hi everyone,
We all know that there is a increase of one degree of HA for an increase of 20mm of fork length. So is there a decrease of one degree in STA along with the increase in HA? I am trying To look at it the other way. Would a one degree decrease in HA increase the STA by one Degree? I have a HT frame with a 65 HA and a 73 STA with a 140mm fork. Hoping to change the fork travel to 120mm to have a 66 HA with a 74 STA to make more XC orientated.
THx for everyone's help

2. Originally Posted by PMaj
Hi everyone,
We all know that there is a increase of one degree of HA for an increase of 20mm of fork length. So is there a decrease of one degree in STA along with the increase in HA? I am trying To look at it the other way. Would a one degree decrease in HA increase the STA by one Degree? I have a HT frame with a 65 HA and a 73 STA with a 140mm fork. Hoping to change the fork travel to 120mm to have a 66 HA with a 74 STA to make more XC orientated.
THx for everyone's help
Since lengthing the fork lifts the front end of the bike, it will decrease both HA & STA by a similar amount.

Likewise shortening the fork will do the opposite.
=sParty

3. You took trig in high school, right? Or did you think you'd have no use for it.

4. Yes, basically, but it's not exactly 1 degree for 20mm, just roughly and will also drop your BB, so don't forget that if you have very rocky/technical trails where pedal strikes might be something to think about.

5. A lot of trail hard tails designed for 140mm travel forks are long low and slack. I would be pretty concerned about lowering the bb.
example is my Pivot Les a XC bike has a higher BB with a 120mm fork then my Santa Cruz Chameleon trail bike with a 140mm fork. Putting a 120 on the SC would cause me to have pedal strikes like mad and the bike still would not handle or ride like my xc bike. where I live is super rocky so clearance might be more an issue for me. Just my thoughts.

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